diff --git a/blkmaker.c b/blkmaker.c
index f7d325c..e1acd6d 100644
--- a/blkmaker.c
+++ b/blkmaker.c
@@ -22,6 +22,15 @@ const char *blkmk_supported_rules[] = {
 	NULL
 };
 
+bool blkmk_supports_rule(const char * const rulename) {
+	for (const char **r = blkmk_supported_rules; *r; ++r) {
+		if (!strcmp(rulename, *r)) {
+			return true;
+		}
+	}
+	return false;
+}
+
 static inline
 void my_htole32(unsigned char *buf, uint32_t n) {
 	buf[0] = (n >>  0) % 256;
diff --git a/blkmaker.h b/blkmaker.h
index 4c2a7d6..809ec6b 100644
--- a/blkmaker.h
+++ b/blkmaker.h
@@ -8,7 +8,8 @@
 #include <blktemplate.h>
 
 #define BLKMAKER_VERSION (5L)
-#define BLKMAKER_MAX_BLOCK_VERSION (4)
+#define BLKMAKER_MAX_BLOCK_VERSION (0x3fffffff)
+#define BLKMAKER_MAX_PRERULES_BLOCK_VERSION (4)
 
 extern bool (*blkmk_sha256_impl)(void *hash_out, const void *data, size_t datasz);
 
diff --git a/blkmaker_jansson.c b/blkmaker_jansson.c
index ecbc52d..cbce12f 100644
--- a/blkmaker_jansson.c
+++ b/blkmaker_jansson.c
@@ -251,10 +251,68 @@ const char *blktmpl_add_jansson(blktemplate_t *tmpl, const json_t *json, time_t
 		}
 	}
 	
-	if (tmpl->version > BLKMAKER_MAX_BLOCK_VERSION || (tmpl->version >= 2 && !tmpl->height))
+	if ((tmpl->version & 0xe0000000) == 0x20000000 && (v = json_object_get(json, "vbavailable")) && json_is_object(v) && (v = json_object_get(json, "rules")) && json_is_array(v)) {
+		// calloc so that a failure doesn't result in freeing a random pointer
+		size_t n = json_array_size(v);
+		tmpl->rules = calloc(n + 1, sizeof(*tmpl->rules));
+		for (size_t i = 0; i < n; ++i) {
+			v2 = json_array_get(v, i);
+			if (!json_is_string(v2)) {
+				return "Non-String data in template rules list";
+			}
+			s = json_string_value(v2);
+			if (s[0] == '!') {
+				++s;
+				if (!blkmk_supports_rule(s)) {
+					return "Unsupported rule strictly required by template";
+				}
+			} else {
+				if (!blkmk_supports_rule(s)) {
+					tmpl->unsupported_rule = true;
+				}
+			}
+			tmpl->rules[i] = strdup(s);
+			if (!tmpl->rules[i]) {
+				return "Memory allocation error parsing rules";
+			}
+		}
+		
+		v = json_object_get(json, "vbavailable");
+		n = json_object_size(v);
+		tmpl->vbavailable = calloc(n + 1, sizeof(*tmpl->vbavailable));
+		struct blktmpl_vbassoc **cur_vbassoc = tmpl->vbavailable;
+		for (void *iter = json_object_iter(v); iter; (iter = json_object_iter_next(v, iter)), ++cur_vbassoc) {
+			v2 = json_object_iter_value(iter);
+			if (!json_is_number(v2)) {
+				return "Invalid type for vbavailable bit";
+			}
+			double bitnum = json_number_value(v2);
+			if (bitnum < 0 || bitnum > 28 || (unsigned)bitnum != bitnum) {
+				return "Invalid bit number in vbavailable";
+			}
+			*cur_vbassoc = malloc(sizeof(**cur_vbassoc));
+			if (!*cur_vbassoc) {
+				return "Memory allocation error for struct blktmpl_vbassoc";
+			}
+			**cur_vbassoc = (struct blktmpl_vbassoc){
+				.name = strdup(json_object_iter_key(iter)),
+				.bitnum = bitnum,
+			};
+			if (!(*cur_vbassoc)->name) {
+				return "Memory allocation error for vbavailable name";
+			}
+		}
+		
+		v = json_object_get(json, "vbrequired");
+		if (v && json_is_number(v)) {
+			tmpl->vbrequired = json_number_value(v);
+		}
+	}
+	else
+	if (tmpl->version > BLKMAKER_MAX_PRERULES_BLOCK_VERSION || (tmpl->version >= 2 && !tmpl->height))
 	{
 		if (tmpl->mutations & BMM_VERDROP)
-			tmpl->version = tmpl->height ? BLKMAKER_MAX_BLOCK_VERSION : 1;
+			tmpl->version = tmpl->height ? BLKMAKER_MAX_PRERULES_BLOCK_VERSION : 1;
 		else
 		if (!(tmpl->mutations & BMM_VERFORCE))
 			return "Unrecognized block version, and not allowed to reduce or force it";
diff --git a/blktemplate.c b/blktemplate.c
index f70f30f..fd990b7 100644
--- a/blktemplate.c
+++ b/blktemplate.c
@@ -117,5 +117,20 @@ void blktmpl_free(blktemplate_t *tmpl) {
 	free(tmpl->workid);
 	free(tmpl->lp.id);
 	free(tmpl->lp.uri);
+	
+	if (tmpl->rules) {
+		for (char **currule = tmpl->rules; *currule; ++currule) {
+			free(*currule);
+		}
+		free(tmpl->rules);
+	}
+	if (tmpl->vbavailable) {
+		for (struct blktmpl_vbassoc **curvb = tmpl->vbavailable; *curvb; ++curvb) {
+			free((*curvb)->name);
+			free(*curvb);
+		}
+		free(tmpl->vbavailable);
+	}
+	
 	free(tmpl);
 }
diff --git a/blktemplate.h b/blktemplate.h
index 263976a..83b92ee 100644
--- a/blktemplate.h
+++ b/blktemplate.h
@@ -78,6 +78,11 @@ extern gbt_capabilities_t blktmpl_getcapability(const char *);
 
 typedef gbt_capabilities_t blkmutations_t;
 
+struct blktmpl_vbassoc {
+	char *name;
+	uint8_t bitnum;
+};
+
 // WARNING: Do not allocate this (ABI is not guaranteed to remain fixed-size)
 typedef struct {
 	uint32_t version;
@@ -123,6 +128,11 @@ typedef struct {
 	int _mrklbranchcount;
 	libblkmaker_hash_t _mrklroot;
 	unsigned int next_dataid;
+	
+	char **rules;
+	bool unsupported_rule;
+	struct blktmpl_vbassoc **vbavailable;
+	uint32_t vbrequired;
 } blktemplate_t;
 
 extern blktemplate_t *blktmpl_create();
diff --git a/private.h b/private.h
index 14eacf1..055061b 100644
--- a/private.h
+++ b/private.h
@@ -7,6 +7,7 @@
 // blkmaker.c
 extern const char *blkmk_supported_rules[];
 extern bool _blkmk_dblsha256(void *hash, const void *data, size_t datasz);
+extern bool blkmk_supports_rule(const char *rulename);
 
 // blktemplate.c
 extern void _blktxn_free(struct blktxn_t *);